How to make particles emit from an object at regular intervals without disappearing the already emitted particles
Here's a workaround that might help. If you don't want to create a particle system for each &quot;pulse&quot; but a single particle system doesn't allow switching emission &quot;on&quot; and &quot;off&quot;, you have to kill particles in those frame ranges that you don't want them.
The lifetime of the particles should be high enough so that they are visible as long as you wish to see them. Let's say you want to emit particles between frames 10-20 and 40-50 for example.

Place a Collision object where the emitter is, set Permmeability = 0 and enable Kill Particles.
Go to frame 9, set keyframes for Permeability and Kill Particles.
Go to frame 10, set Permeability = 1 and disable Kill Particles and keyframe those values again.
Go to frame 20, set keyframes again without changing the values.
On frame 21, set Permeability = 0 and enable Kill Particles, keyframe them again.
Select all keyframes in the Timeline, Ctrl+C to copy them, then go to frame 39 and paste them with Ctrl+V
Keep pasting those keyframes wherever you want to emit particles on the Timeline.

Timeline example for Collision object:

Now here comes the problem: depending on what kind of scene you have and how and where you want the particles to emit, killing the particles normally takes (at least) one frame, so they exist for one frame and will be visible. If your scene setup allows it, you could disguise this by having the emitter hidden by another object so that those killed particles stay inside there.
If you are rendering with Cycles you can use the Age output of the Particle Info in the Shader Editor for the particle material. Plug Age into a Greater Than node to check if Age &gt; 1. This information can be used as a Mix Factor between a Transparent Shader and the normal particle material, this makes the particles appear at an age of &gt; 1. This is probably the best, because you can hide the Collision object and don't need another object hiding the killed particles.